This invention relates to an apparatus and method for facilitating the connection of tubulars using a top drive and is, more particularly but not exclusively, intended for facilitating the connection of a section or stand of casing to a string of casing.
In the construction of oil or gas wells it is usually necessary to line the borehole with a string of tubulars known as casing. Because of the length of the casing required, sections or stands of say two or three sections of casing are progressively added to the string as it is lowered into the well from a drilling platform. In particular, when it is desired to add a section or stand of casing the string is usually restrained from falling into the well by applying the slips of a spider located in the floor of the drilling platform. The new section or stand of casing is then moved from a rack to the well centre above the spider. The threaded pin of the section or stand of casing to be connected is then located over the threaded box of the casing in the well and the connection is made up by rotation therebetween. An elevator is then connected to the top of the new section or stand and the whole casing string lifted slightly to enable the slips of the spider to be released. The whole casing string is then lowered until the top of the section is adjacent the spider whereupon the slips of the spider are reapplied, the elevator disconnected and the process repeated.
It is common practice to use a power tong to torque the connection up to a predetermined torque in order to make the connection. The power tong is located on the platform, either on rails, or hung from a derrick on a chain. However, it has recently been proposed to use a top drive for making such connection.
Because of the high costs associated with the construction of oil and gas wells time is critical and it has been observed by the applicants that the time to connect a tubular to a top drive using existing equipment could be reduced.
It has been observed that sections or stands of tubulars are often not as uniform as desired. In particular, the sections or stands of tubulars are often not straight. The top drive is in perfect alignment with the centre of the spider in the platform of an oil or gas rig. However, a section or stand of tubulars located in the spider would not always be in alignment with the top drive.
There is described an apparatus and method for facilitating the connection of tubulars using a top drive in co-pending UK Patent Application No. 98 18363.5, which apparatus comprises a stator attachable to the top drive and a supporting member for supporting a tool wherein means are provided to allow substantially horizontal movement of said supporting member.
The apparatus disclosed therein is bulky, cumbersome and awkward to use. The present invention attempts to reduce these problems.
Accordingly, there is provided an apparatus for facilitating the connection of tubulars using a top drive, the apparatus comprising a supporting member for connection with said top drive, a tool for gripping a tubular and means for allowing substantially horizontal movement therebetween wherein said means comprises a flexible membrane enclosing a fluid.
Other features of the invention are set out in claims 2 to 15.
There is also provided a method for facilitating the connection of tubulars, the method comprising the steps of moving a tool for gripping a tubular substantially in a horizontal plane relative to a supporting member whereupon a flexible membrane located therebetween is deformed.